The present invention relates to a false-twist texturing method of a yarn including poly lactic acid fiber (PLA) which is manufactured from poly lactic resin of which the raw material is the lactic acid obtained from starch of the corn or the like.
Conventionally, a false-twist texturing method wherein synthetic fiber filament yarn of polyester yarn or the like unwound from a yarn supplying package is inserted through a first heater which is heated more than or equal to approximately 120xc2x0 C., false-twisted by a friction typed false-twisting device provided in the downstream side to the first heater, and then after inserted through a second heater for reducing a yarn torque, wound into a package via an oiling device or the like accordingly, is known.
Recently, from the aspect of the environment, a yarn of which the raw material is the poly lactic acid fiber has been paid attention and such yarn has been attempted to be textured with a false-twist.
However, the poly lactic acid fiber is weak against heat and friction, and the elasticity and the strength is also low. Therefore, when false-twist texturing is carried out to such fiber under the same conventional condition, there was a problem in that a yarn breakage occurred frequently.
It is thus the object of the present invention to provide a false-twist texturing method capable of applying false-twist texturing to the yarn including at least the poly lactic acid fiber without causing the yarn breakage frequently.
To accomplish the object mentioned above, a false-twist texturing method of the present invention is characterized in that a yarn including the poly lactic acid fiber is fed through a first feed roller, a first heater, a false-twisting device and a second feed roller in this order, and the yarn is to be textured with false-twist under the condition in which the heating temperature of the first heater is set lower than or equal to 130xc2x0 C. According to the false-twist texturing method, it is preferable to set the heating temperature of the first heater to be lower than or equal to 110xc2x0 C. Moreover, the first heater is preferable to be a contacting typed heater comprising a heat plate where the running yarn contacts. In addition, the contacting length of the yarn to the contacting typed heater is preferable to be shorter than or equal to two meters.
Moreover, the false-twisting device is preferable to be a nip typed false-twisting device. Furthermore, a balloon control plate is to be provided between the first heater and the false-twisting device, and a yarn guide is to be provided between the balloon control plate and the first heater, and it is preferable to bend the yarn by the yarn guide. In addition, a plurality of yarn guides are to be provided, and the yarn guide located at the first heater side among the plurality of yarn guides is preferable to be a rotatable yarn guide.